/Engine/Plugins/Runtime/GeometryCache/Source/GeometryCache/Private/GeometryCacheStreamingManager.h
Releases pointer to a chunk of cahed geometry data. Can be called from any thread. Should be called for every call to MapChunk.
void UnmapChunk ( const [UGeometryCacheTrackStreamable](API\Plugins\GeometryCache\UGeometryCacheTrackStreamable) * Track, uint32 ChunkIndex )